This invention relates to apparatus for gripping a work piece which is to be moved or worked on by a remotely operated or automatically operated machine. This is the area of art commonly referred to as "robotics."
It is common in this field to grip a work piece externally or internally by means of a gripper actuated by a power device such as a hydraulic or pneumatic cylinder, solenoid or the like. This operation is commonly of a repetitive nature in which identical work pieces are operated on by the gripper in succession. The force applied by the gripper to the work piece must be adequate to hold it firmly but in many operations it is important that the gripper not deform or mar the work piece. Therefore, the ability of the gripper to adjust to a precise aperture and to maintain the adjustment over a series of successive operations is critical. However, with most devices in the prior art, the adjustment must be done by trial and error. That is, the initial adjustment is made by measurement or estimate with the gripper stationary or inoperative. Then the gripper is tried, readjusted as necessary and tried again and so forth. Because of the location or nature of the adjusting means, grippers of the prior art cannot be adjusted while they are actually in operation. Therefore, a precise adjustment, taking into account free play, backlash and other relevant factors, cannot be made.